In general, in a gravure coater, a coating is supplied to an engraved portion of a gravure roll, and the coating deposited in the engraved portion is applied to a web. In order to provide a high grade of such an application finish, the coating must be supplied uniformly to the engraved portion of the gravure roll.
To this end, it is a conventional practice to immerse only a lower portion of an ink roll into a coating stored in an upwardly opened pad without direct immersion of the gravure roll into the coating, and rotate the ink roll to take up the coating while depositing it onto the ink roll, thereby supplying the coating to the gravure roll in contact with the ink roll, for example, as described in Japanese Utility Model Publication Nos. 19601/77 and 38276/82.
In the prior art, however, a coating classified into a Newtonian fluid having a small viscosity is uniformly supplied to the gravure roll, but a magnetic coating or the like which presents a gel in a normal condition could not be uniformly supplied to the gravure roll. This results in a failure to apply the coating with a uniform thickness to the web, providing a degraded application finish. Some of the coatings in the form of a mixture of a plurality of components, such as those containing easily precipitatable components and those comprising components easily separatable from each other, should be applied to the web in such a condition that the individual components have been uniformly mixed together. In the prior art, it has been difficult to supply such coatings to the gravure roll in a condition of the individual components uniformly mixed together.
Thereupon, a lower end of an outer peripheral surface of the gravure roll has conventionally been immersed into the coating within the pad, so that the coating may be supplied to the gravure roll while being permitted to overflow in a large amount out of the pad to the outside.
However, the prior art is accompanied by disadvantages that there is a wasteful coating and that when the overflowed coating is to be reused, a volatile component or components can scatter from the coating at overflowing, resulting in a very troublesome adjustment of the viscosity of the coating in the pad.
In addition, a pump has been placed for feeding the coating into the pad, apart from the pad portion. When the coating to be gravure-applied is changed, however, the specially placed pump of a complicated structure must be also thoroughly cleaned, resulting in a failure to rapidly conduct, for example, a color overchange or the like.